A 72-year-old male patient, previously healthy, was admitted with fever, asthenia and pain in the right gluteal region at the site of a prior intramuscular corticosteroid injection. He had fever, tachycardia and laboratory tests showing leukocytosis with left shift, renal dysfunction, and elevated C-reactive protein and lactate levels. Blood cultures were collected and ampicillin-sulbactam was started. Pelvic magnetic resonance imaging showed pyomyositis with a large abscess in the gluteus medius and minimus muscles, extending to the adductor longus and iliopsoas. Surgical debridement with fasciotomy and culture collection was performed. Due to the severity of the condition, empirical daptomycin was added to the antimicrobial regimen. Intraoperative cultures identified methicillin-susceptible Staphylococcus aureus (MSSA), and therapy was de-escalated to cefazolin. The patient improved clinically and was discharged on sulfamethoxazole-trimethoprim to complete six weeks of treatment at home. Pyomyositis is a bacterial intraparenchymal infection of skeletal muscle, characterized by abscess formation and also known as tropical pyomyositis. The main pathogen involved is Staphylococcus aureus, and the frequently affected sites are the large muscles of the lower limbs. It is more often seen in immunosuppressed individuals. Mortality ranges from 0.89% to 23%, and early diagnosis is the most effective intervention to minimize disease complications. In advanced stages, fever and myalgia/claudication are the most common symptoms, sometimes associated with bacteremia and sepsis, toxic shock syndrome or osteomyelitis (by contiguity or hematogenous spread). In resource-limited settings, the diagnosis of pyomyositis is based on clinical presentation and ultrasound, although magnetic resonance imaging is the gold standard. Primary treatment regimens include anti-staphylococcal penicillins in suspected or confirmed MSSA infections. In suspected or confirmed MRSA, vancomycin, linezolid or daptomycin are indicated. In suspected anaerobic involvement, metronidazole is recommended. Surgical drainage is indicated for all patients. Treatment duration ranges from 2 to 4 weeks, depending on clinical response, with the possibility of switching to oral therapy if evolution is favorable.
Vasconcellos et al. (Sun,) studied this question.